How can electrical resistivity tomography help in site characterization?

• A. It images subsurface conductivity contrasts, helping delineate lithology, moisture content, and potential contaminant zones
• B. It measures surface temperature
• C. It directly samples groundwater
• D. It visualizes chemical gradients

Answer: (A)

Electrical resistivity tomography maps how easily electricity moves through the subsurface, producing images of resistivity contrasts. Resistivity depends on lithology, water content, porosity, and the amount of dissolved ions. Because of that, ERT can reveal where different materials lie (for example, clay versus sand), show changes in moisture content and saturation, and highlight zones where contaminants alter ionic content. In site characterization, this helps delineate lithologic boundaries, identify saturated versus unsaturated regions, and trace potential contaminant plumes before targeted sampling.